Composite floor construction



6, 1969 R. E. ALBRECHT ET AL 3,462,902

COMPOS ITE FLOOR CONSTRUCTION Filed Dec. 20. 1965 //VV'/V7'0/\5. RAYMONDE. ALBRECHT, BERNARD E. CURRAN ROBERT G. LINDNER United States Patent3,462,902 COMPOSITE FLOOR CONSTRUCTION Raymond E. Albrecht and BernardE. Curran, Sewickley,

and Robert G. Lindner, Bridgeville, Pa., assrguors to H. H. RobertsonCompany, Pittsburgh, Pa., a corporation of Pennnsylvania Filed Dec. 20,1965, Ser. No. 514,976

Int. Cl. E04!) 5/16, 13/04 U.S. Cl. 52336 3 Claims ABSTRACT OF THEDISCLOSURE A composite floor construction utilizing corrugated sheetmetal decking and concrete. The allowable loading for a specific span ofcomposite flooring is significantly increased by the inclusion of wiresor mesh embedded in the concrete in those regions where the deckingrests upon a horizontal beam of the building framework. The quantity ofwires or mesh is insufficient to satisfy the requirements of theAmerican Concrete Institute for shrinkage and temperature reinforcementof concrete generally.

This invention concerns composite floor construction utilizingcorrugated sheet metal decking and concrete.

PRIOR ART In the construction of many multi-story buildings, the floorsare assembled from corrugated sheet metal decking which is rigidified bya covering concrete layer. Such floor construction is described in U.S.Patents 1,855,082, 2,259,674. The concrete component of such floorconstruction is considered as a parasitic mass making no contributionwhatsoever to the load carrying capability of the building floor. Thecorrugated metal decking sustains the entire load including the weightof the concrete.

There are other floor constructions utilizing corrugated sheet metaldecking merely as a form for supporting a poured-in-place reinforcedconcrete slab which serves as a building floor, 1,073,540; 1,073,542.Such concrete slabs combine the hardened concrete with metal tensionreinforcement rods or wires.

More recently various proposals have been advanced for utilizing theload carrying capability of concrete components in combination with theload carrying capability of the sheet metal decking elements. The twomaterials are combined and the resulting floor has been identified as acomposite floor. Typical composite floor construction has been describedin Canada Patents 704,839; 704,- 840; 704,841 and 704,842. All of thesecomposite floor constructions utilize corrugated sheet metal deckinghaving alternating crests and valleys with generally vertical webstherebetween. The sheet metal decking extends generally horizontallybetween the horizontal beams of the building framework and is coveredwith concrete to form a composite floor construction. The crests of suchcorrugated metal fiooring sections are deformed from a plane, preferablyby indented or embossed grooves which are transverse to the longitudinalaxis of the decking sections. The decking also has some means to retainthe covering layer of concrete in tight engagement with the deckingsections. This hold-down means may take the form of diverging webs asdescribed in Canada Patents 704,839 and 704,840; or may take the form ofdeformations such as indentations or embossments along the vertical webgenerally parallel to'the longitudinal axis of 3,462,902 Patented Aug.26, 1969 THE PROBLEM The provision of greater allowable loadings forcertain span lengths with such composite fioor constructions wouldextend the applicability of such flooring constructions. Conversely, forconstant allowable loadings, greater spans might be realized.

THE PRESENT INVENTION According to the present invention, we havediscovered a surprising means which achieves an increase ofapproximately 66% in the allowable loading for a specific span ofcomposite flooring.

The composite flooring of this invention utilizes the compositecorrugated sheet metal flooring sections as described in theabove-mentioned Canada patents. Those flooring sections extend acrossthe horizontal beams of the building. A supply of metal wires or mesh isprovided above the corrugated metal decking in those regions where thedecking rests upon a horizontal beam of the building framework. Themetal wires or mesh are displaced above and out of engagement with thecorrugated metal decking. The metal wires or mesh are embedded in theconcrete cover which is subsequently poured above the structure. Inorder to support the metal wires or mesh above the corrugated metaldecking prior to the pouring and hardening of the concrete, suitablewire chairs or other non-structural spacer members may be provided.

The unexpected feature of the present invention is the remarkableincrease in allowable loading (at constant span) which can be achievedby the inclusion of such metal wires or mesh in the present compositefioor structure. Non-composite corrugated metal flooring sections, forexample, of the type described in U.S. Patent 1,855,- 082, produce afioor which is unaffected in its loadsupporting characteristics by thepresence or absence of such wires or mesh in the concrete. Suchnon-composite fioors are designed so that the steel decking supplies theentire load carrying requirements of the floor. The concrete is nottaken into consideration and hence any modifications to the concretecomponent do not affect the load carrying capacity of the resultingfloor.

The wires or mesh contemplated by the present invention are insufiicientto satisfy the requirements of the American Concrete Institute Code forshrinkage and temperature reinforcement of concrete generally. Suchshrinkage and temperature reinforcement of concrete slabs is merelyauxiliary to the principal metal reinforcement of reinforced concreteslabs. Hence the wires or mesh contemplated by the present invention(insufiicient to serve even as shrinkage or temperature reinforcement)does not create any reinforced concrete slabs in combination with theconcrete.

It is therefore wholly unexpected that the use of such lightweight metalwires or mesh in the concrete layer of composite decking should sosubstantially alter the load carrying capacity of the resulting floor.The wires or mesh contemplated by the present invention are not theconventional reinforcing rods, wires or mesh which are familiar astensile components of reinforced concrete slabs. Such prior artreinforcing rods, wires or mesh are required to sustain substantialtensile stresses in slabs where the concrete sustains compressivestresses. The present wires or mesh are required, moreover, only acrossthe supporting beams, which further distinguishes the present conceptfrom the prior art.

The amount of metal in the present wires or mesh is less than thatspecified as shrinkage and temperature reinforcement for concrete. Thusthe metal wires or rods of the present invention are not adequate insize to serve as concrete reinforcement and are inadequate in size toserve even as shrinkage and temperature mesh for the concrete slab. Infact, the present metal wires or mesh are of such size that the concreteslab is allowed to develop cracks in the regions above the supportingbeams.

The present invention, its objects and advantages will be more clearlyunderstood by the following detailed description which refers to theaccompanying drawings in which:

FIGURE 1 is a perspective illustration of a typical multi-story buildingutilizing composite fioor construction principles;

FIGURES 2, 3, 4, 5 are fragmentary perspective illustrations of typicalcorrugated metal decking sections of the type with which the presentinvention is concerned;

FIGURE 6 is a cross-section illustration taken along line VI-VI ofFIGURE 1 illustrating the principles of the present invention; and

FIGURE 7 is a fragmentary illustration of metal wire mesh fabricatedfrom steel wires.

Referring to FIGURE 1 there is illustrated a building 10 having verticalcolumns 11 and horizontal beams 12. Corrugated sheet metal decking 13 isprovided above the beams 12 and is covered with a layer 14 of concretewhich serves as a rigidifying floor component.

In order to achieve composite coaction between the sheet metal decking13 and the covering concrete layer 14, the decking may be provided inthe configuration shown in FIGURES 2, 3, 4, 5. The sheet metal deckingshown in FIGURES 3 and 5 is of a special type known as metal cellularflooring.

Referring to FIGURE 2, the sheet metal decking section 19 is the typeshown in Canada Patent 704,841. It comprises a metal sheet havingalternating crests 20, valleys 21 and sloping webs 22. The crests 20 areprovided with deformations 23 which are preferably elongatedindentations as shown in FIGURE 2 although the deformations 23 maycomprise elongated embossments or weld beads. In general thedeformations 23 extend transversely to the axis XX of the metal deckingsection 19. A plurality of elongated deformations 24 is provided alongthe generally vertical webs 22 in a direction parallel to the axis XX.The deformations 24 are preferably embossments as shown but may beindentations or weld beads.

The metal cellular flooring section 28 shown in FIG- URE 3 correspondsto that described in Canada Patent 704,842 and includes a top sheet 29and a bottom sheet 30 which are joined together by a plurality of spotwelds 31. The top sheet 29 has alternating crests 32 and valleys 33 withintervening sloping webs 34. Deformations 35 are provided along thecrests 32 corresponding to the deformations 23 discussed in connectionwith FIGURE 2. Elongated deformations 36 are provided along the slopingwebs 34 corresponding to the elongated deformations 24 described inconnection with FIGURE 2. The bottom sheet 30 is essentially flat.Lengthwise cells 37 are presented in the metal cellular flooring section28 of FIGURE 3 to serve as raceways for distribution of electricalwiring and ventilation air. Each cell is defined by a portion of thebottom sheet 30, the undersurface of a crest 32 and the inner surfacesof adjoining vertical webs 34.

An alternative sheet metal decking section 39 suitable for compositecoaction in a floor construction is illustrated in FIGURE 4corresponding to that described in Canada Patent 704,839. The corrugatedmetal decking 39 of FIGURE 4 includes alternating crests 40 and valleys41 with converging vertical webs 42. The vertical webs 42 convergedownwardly from the sides of each of the crests 40 whereby the channels43 which are formed between adjacent crests 40 are wider at the bottomalong the valley 41 than along the top. These valleys 43 serve toconfine a subsequently poured layer of concrete and maintain thehardened concrete in engagement with the corrugated decking sections 39.Accordingly with the configuration shown in FIGURE 4 there is no needfor elongated deformations of the type identified by the numeral 24 inFIGURE 2.

Deformations 44, provided along the crests 40 correspond in functionwith the deformations 23 already described in connection with FIGURE 2.The deformations 44 are disposed transversely to the longitudinal axisXX of the corrugated decking section 39.

A metal cellular flooring section 49, shown in FIG- URE 5, correspondswith that described in Canada Patent 704,840. This metal cellularflooring section 49 comprises a top sheet 50 and a bottom sheet 51. Thetop sheet 50 corresponds with the corrugated sheet metal decking section39 already shown in FIGURE 4 and includes alternating crests 52, valleys53 and converging webs 54. The top sheet 50 is secured to the bottomsheet 51 by a plurality of spot welds 55 which are disposed along thevalleys 53. Deformations 56, provided along the crests 52, correspond infunction with the deformations 23 already described in connection withFIGURE 2. The converging webs 54 define alternating channels 57 betweenthe adjacent crests 52. The channels 57 are wider at the bottom alongthe valleys 53 than along the top. The metal cellular flooring section49 includes longitudinal cells 58 corresponding to the longitudinalcells 37 described in connection with FIGURE 3. The longitudinal cells58 likewise may serve as raceways for distribution of electrical wiringor ventilation air.

The four decking sections shown in FIGURES 2, 3, 4, 5 all possessalternating crests and valleys with generally vertical webstherebetween. The sections have deformations in the crests extendingtransverse to the longitudinal axis of the decking. The sections possesshold-down means which comprises converging vertical webs (FIGURES 4, 5)or non-converging webs with linear deformations (FIGURES 2, 3).

The assembly of corrugated sheet metal decking sections according to thepresent invention is illustrated in FIGURE 6 wherein the sheet metaldecking 13 is applied over horizontal building beams 12a, 12b, 120. Thesheet metal decking 13 adopts a normal sag between the beams 12a, 12b,12c. An effective composite floor construction can be obtained byutilizing as the decking 12 any of the sheet metal corrugated flooringsections shown in FIG- URES 2, 3, 4, 5 in combination with a coveringlayer of concrete as described in the above-mentioned Canada patents.However by providing metal mesh 15 within the concrete layer 14 aboveand across each of the horizontal beams 12a, 12b, 120, a strikingincrease in the load carrying capability of the resulting building flooris achieved. The metal mesh 15 is not connected to the corrugated metaldecking 13, but instead, is displaced above the crests of that deckingand below the top surface of the concrete 14. Metal reinforcing rods andmesh in concrete construction frequently are supported by small wirechairs which serve the sole purpose of elevating the metal reinforcingrods to a predetermined level above the bottom of a concrete form. Suchwire chairs are contemplated for the purpose of elevating the metalreinforcing wires and mesh 15 above the ,crests of the corrugated metaldecking 13 without introducing any structural connection between themesh 15 and the decking 13.

The metal mesh 15 is similar to the familiar temperature reinforcementor shrinkage reinforcement material which is utilized in concretestructures, but contains less metal. Such shrinkage and temperature meshis described in the American Concrete Institute Code, Section 807, 1963edition, as follows:

807-Shrinkage and temperature reinforcement (a) Reinforcement forshrinkage and temperature stresses normal to the principalgcinforcementshall be provided in structural floor and roof slabs where the principalreinforcement extends in one direction only.

Such reinforcement shall provide at least the following ratios ofreinforcement area to gross concrete area,

but in no case shall such reinforcing bars be placed farther apart thanfive times the slab thickness or more than 18 in.

Slabs where plain bars are used 0.0025 Slabs where deformed bars withspecified yield strengths less than 60,000 p.s.i. are used 0.0020 Slabswhere deformed bars with 60,000 p.s.i. specified yield strength orwelded wire fabric having welded intersections not farther apart in thedirection of stress than 12 in. are

used 0.0018

Thus where welded mesh is utilized for shrinkage and temperaturereinforcement under the ACI Code, the metal cross-section is greaterthan.0.00l8 times the concrete cross-section. A lesser amount of wiremesh is contemplated for the present invention since development ofconcrete cracking is anticipated, is intended, and is not avoided.

Customary wire mesh is assembled by arranging individual Wires in acriss-cross basket weave pattern and welding the points of intersectionto form a checkerboard like structure which is widely used astemperature and shrinkage reinforcement in concrete slabs. Suchreinforcing mesh usually is available in various wire sizes and wirespacings. For the present invention, ordinary welded wire fencing iscontemplated. Provision of the metal wires or mesh 15 in lesserquantities than the temperature and shrinkage reinforcement requirementsof the American Concrete Institute Code achieves the present unexpectedimprovements. Such typical reinforcing mesh is illustrated in FIGURE 7as including a number of generally parallel wires 61 which areinterwoven with a second series of generally parallel wire 62. At eachintersection 63 there is a weld connection between the wires 61, 62 toform a rigid open fabric 60 known in the construction industry as wiremesh.

EXAMPLES Two corrugated metal decking sections were tested todemonstrate the effect of metal mesh in the concrete covering layer forcomposite sheet metal corrugated decking above the supporting beams.Examples 2 and 4 correspond to this invention. Examples 1, 3, 5, 6illustrate prior art.

Example 1.A metal cellular flooring section of the type shown in FIGURE3 was tested. The bottom sheet 30 was fabricated from 16 gauge steel.The top sheet 29 was fabricated from 18 gauge. Each flooring section was24 inches side-to-side and contained a total of 4 crests and hence 4cells. The crest widthwas 3.875 inches. The valleys were 2.125 incheswide. The height of the crests above the valleys was 1.5 inches (insidedimension). The crest deformations 35 were indentations as described inoccurred at a load of 1300 pounds per square foot (live June 18, 1965,and assigned to the assignee of this invention. The longitudinal webdeformations 36 (FIGURE 3) were embossments as described in that patentapplication. The metal cellular flooring was supported on knife edges 12feet apart, creating a span of 12 feet. The flooring section was coveredwith 2 /2 inches of concrete above the crests of the decking. Theconcrete had a compressive strength of 2610 p.s.i. Prior to pouring theconcrete, a film of grease was applied to the metal decking to preventformation of any adhesive bond between the decking and the concrete.

After the concrete had hardened, loads were applied to the flooringstructure. Failure of the structure occurred at a loading of 475 poundsper square foot (live load). For this purpose the term failure isdefined as the inability of the flooring assembly to accept additionalload.

Example 2.-The corrugated metal decking sections described in Example 1were provided in lengths of 14.5 feet. A section was supported on 6 inchWF beams at its ends and its mid-point. Thus the free span of theresulting floor was 7 feet 3 inches. The flooring was covered with alayer of concrete to a depth of 2.5 inches above the crests of thedecking. A section of welded metal mesh 2 feet wide by 14.5 feet long,was applied to wire chairs above the decking before the concrete waspoured. A film of grease was applied to the metal decking prior topouring the concrete to prevent formation of any adhesive bond betweenthe decking and the concrete. The concrete had a compressive strength of2755 p.s.i. The welded metal mesh was in the form of 6 inch squares ofNo. 10 Wire having a diameter 0.135 inch, weighing 0.21 pound per squarefoot. The reinforcing mesh extended across the entire metal flooringsection above the central beams. The mesh was one inch below the levelof the concrete, i.e., 1.5 inches above the crests of the decking.

Upon application of the load, failure of the structure occurred at aload of 1300 pounds per square foot (live load).

Example 3.-The properties of ordinary unindented, unembossed metalcellular flooring are well known, being described in many catalogs as aresult of numberless tests and actual installations. The properties ofsuch sections are readily calculable. Calculations were carried out foran ordinary, unindented, unembossed metal cellular flooring sectionotherwise identical in dimensions to that of Example 1. Such section wasassumed to be supported on 6 inch WF beams over a span of 7 feet 3inches. The flooring was assumed to be covered with 2.5 inches of p.s.i.concrete above the tops of the crests. Upon application of load, failurewill occur at a loading of 202 pounds per square foot (total load). Theweight of the concrete and decking alone (dead load) is 43.3 pounds persquare foot. Accordingly the calculated live load at failure is 158.7pounds per square foot.

This example assumes a yield strength of the sheet steel at 33,000 psi,and also assumes that no adhesive bond develops between the concrete andthe steel decking.

Example 4.Example 3 is duplicated assuming that welded metal mesh asdescribed in Example 2 is applied to chairs over the supporting beam.There can be no change in the failure load for this test since the steeldecking alone sustains the design load.

Example 5.The unindented, unembossed metal cellular flooring sectiondescribed in Example 3 was assumed in a 12 foot span and covered withconcrete to a depth of 2.5 inches above the crests. Failure of thespecimen will occur at 74 pounds per square foot (total load)corresponding to 30.7 pounds per square foot (live load).

Again the yield strength of the steel sheet is assumed to be 33,000p.s.i. and it is further assumed that no adhesive bond develops betweenthe steel decking and the concrete.

Example 6.The failure of the 12 foot span also will occur at about 74pounds per square foot when a quantity of welded metal mesh is providedas described in Example 2 above the corrugated metal decking, since thesteel decking alone sustains the design loads.

The results of the foregoing examples are tabulated in the followingTable I.

TABLE I.ALLOWABLE LOADS OF FLOORINGASSEMBLIES WITH CORRUGATED METALDECKING AND CONCRETE [Allowable loading, p.s.f.]

The allowable loading values shown in Table I are determined, inaccordance with conventional design practices, by applying a safetyfactor of 2.0 to the actual failure load. Those figures followed by anasterisk are the values obtained from the Examples 16. The values markedwith double asterisks in Table I were obtained by conventional designcalculations for the changes in span. That is, the value 393 wasobtained by relating the value 237.5 (based on a 12.0 foot span) to thecorresponding value for a span of 7.25 feet; similarly the value 390 wasobtained by relating the value 650 (for a span of 7.25 feet) to acorresponding value for a 12.0 foot span.

It will be observed from study of Table I that the use of thereinforcing material with the present composite decking achieves aremarkable increase in the allowable loading of the resulting floor,namely, a 66% increase above that which could be achieved in the absenceof the metal mesh. The metal mesh alone is not responsible for thechange as is evidenced in Table I where the mesh contributes noimprovement whatsoever to the ordinary corrugated metal decking.

GENERAL OBSERVATIONS The present improvement appears to be unique withthose composite corrugated sheet metal decking sections havingtransverse deformations in the crests. Such corrugated metal deckingsections are described in the aforesaid Canada Patents 704,839; 704,840;704,841 and 704,842. In addition these composite sheet metal deckingsections have a hold-down means which may comprise linear deformationsalong the vertical webs of the deck-ing as shown in FIGURES 2 and 3 ormay comprise converging webs as shown in FIGURES 4 and 5. The presentimprovement in load carrying capability of composite flooring structuresis not manifested with other types of corrugated sheet metal deckingsections.

The unique feature of the described composite sheet metal deckingresults from (a) the provision of alternating crests and valleys havinggenerally vertical webs therebetween; (b) the provision of deformationsin the crests of the decking; (c) the provision of a hold-down meanswhich may comprise deformations in the webs of the decking or convergingwebs; (d) the provision of metal wires or welded mesh in the coveringconcrete layer above the crests of the decking at least in the regionswhere the decking rests on horizontal beams.

We claim:

1. In a building having a composite floor construction including:horizontal beams; corrugated sheet metal decking having alternatingcrests and valleys and generally vertical webs converging from each ofsaid crests toward the adjoining valleys and extending lengthwisebetween the said horizontal beams; a concrete covering over the saiddecking; deformations in the said crests of the said decking extendingtransverse to the longitudinal axis of said decking; said concreteconforming to the said deformations and said converging vertical webs;the improvement comprising:

metal wires in the said concrete spaced apart from the said deckingabove each of the said horizontal beams; the said metal wires beingprovided in a quantity which is insufficient to satisfy the requirementsof the concrete for temperature and shrinkage reinforcement.

2. In a building having a composite floor construction including:horizontal beams; corrugated sheet metal decking having alternatingcrests and valleys and generally vertical webs therebetween andextending lengthwise between said horizontal beams; a concrete coveringover the said decking; deformations in the said crests of the saiddecking; deformations in the said webs of the said decking; saidconcrete conforming to the said deformations; the improvementcomprising:

metal wires in said concrete spaced apart from said decking above eachof said horizontal beams, the quantity of said metal wires beinginsufficient to satisfy the requirements of the concrete for temperatureand shrinkage reinforcement.

3. The improvement of claim 2 wherein the said metal wires comprise awelded metal mesh.

References Cited UNITED STATES PATENTS 602,274 4/1898 Sill 52-339840,016 1/1907 Schlafly 52 450 1,073,906 9/1913 Kahn 52 577 1,170,7432/1916 Evers 52 675 1,986,171 1/1935 Wilson 52 336 2,256,309 8/1944Garbe 52 450 3,245,186 4/1966 Jentoft 52 334 3,283,458 11/1966 Gersovitz52-260 FOREIGN PATENTS 278,186 10/1927 GreatBritain.

FRANK L. ABBOTT, Primary Examiner J. L. RIDGILL, JR., Assistant ExaminerUS. Cl. X.R. 52452

